Maritime archaeological investigator Barry Clifford points to a cannon illustration as he talks in New York about Christopher Columbus' flagship, the Santa Maria.

Photo: Don Emmert, AFP/Getty Images

Maritime archaeological investigator Barry Clifford points to a...

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Maritime archaeological investigator Barry Clifford talks about discovering what he believes to be Columbus' ship, the Santa Maria off the northern coast of Haiti at a news conference May 14, 2014 in New York. Clifford says "all the geographical, underwater topography and archaeological evidence strongly suggests that this wreck is Columbus' famous flagship, the Santa Maria," which struck a reef and foundered on Christmas Day in 1492. AFP PHOTO/Don EmmertDON EMMERT/AFP/Getty Images

A shipwreck off northern Haiti may be the remains of Christopher Columbus' flagship vessel the Santa Maria, an explorer said Wednesday, though experts expressed caution about a discovery that was far from confirmed.

Explorer Barry Clifford was in New York on Wednesday to show video of the underwater wreckage of the Santa Maria, which ran aground on Christmas Day 1492.

Clifford showed photos and video of what he said was a pile of ballast stones that appear to have come from Spain or Portugal and what looks like a 15th century cannon from the wreckage. He said the wreckage has been looted and needs to be excavated immediately.

Clifford, known for discovering a pirate ship off Cape Cod in 1984, said another factor is the location of the wreckage, in about 15 feet of water near where the crew of the Santa Maria is thought to have built a coastal settlement for crew members of the ship who were left behind after the sinking.

"The circumstantial evidence is overwhelming," Clifford said. "The cannon is the smoking gun, so to speak."

He said that he and his son, Brandon, first explored the site and took photos in 2003. They decided to publicize their findings after a follow-up dive and examination of the photos led them to conclude they may have found the Santa Maria. The cannon that they saw in 2003 had vanished by the time they returned last week.

Clifford, whose exploration of the site is being backed by the History Channel, says he has asked the Haitian government to preserve the area around the wreck. "The next step is a careful, thorough and timely excavation," he said.

Salim Succar, a special adviser to Prime Minister Laurent Lamothe, said the government will do "all that is needed" to protect the site "while deciding on the best options to feature this discovery."

If the ship is the Santa Maria, it would be the oldest known European shipwreck in the so-called New World and a find of major archaeological significance. But scientists say it's far too early to make any such declaration, especially since there is likely to be very little left of the vessel.

"The evidence, as you can imagine, after more than 500 years is not going to be very much because of time and the environment that the site is in," said Roger Smith, the state underwater archaeologist for Florida. "It's going to require some careful archaeology."

Smith said it's possible the ship found by Clifford is the Santa Maria, but he noted that there was at least one wreck in that area that was once mistakenly thought to the ship but turned out to be a much later vessel.